I also have the Lacie d2 250 GB HD. I like it, but I basically use it just to back up with. It is not too noisey, but you do know when it is on and spinning. Not sure about a fan, but you do hear the drive. Since it is FW I was curious as to weather it was faster to boot or run from, so I tried it. For how I use it, I didn't notice any difference in boot speed or in practical useage from the 4200 RPM int.